Co–Mn Mixed Metal Oxide Nanorods for On-Site Colorimetric Detection of SO₃^2– in Food Samples

Abstract

Excessive sulfite (SO3 2–) causes serious human health problems, making its detection highly valuable. In this work, a colorimetric sensor was presented for the detection of SO3 2– on the basis of Co–Mn mixed metal oxide (CoMn MMO) nanorods. CoMn MMOs composed of CoMn2O4 were uniformly dispersed among Co3O4 by calcining Co6(CO3)2(OH)8·H2O@CoMn2O4 nanorods in air, which had intrinsic oxidase-like activity. The synergistic introduction of CoMn2O4 promoted electron transfer in Co3O4, which not only prevented the aggregation problem but also increased the active sites, and the catalytic activity of the resulting CoMn MMO nanoenzyme was significantly enhanced. The obtained nanocomposites could catalyze the oxidation of the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxTMB with a quite low Michaelis–Menten constant (K m) of 0.042 mM and a quick V max of 0.85 × 10–8 M s–1 by generating a superoxide radical (·O2 –). Based on the inhibitory effect of SO3 2– on the CoMn MMOs-TMB system, the proposed method allowed for SO3 2– detection with the linear concentration range from 1.56 to 15.58 μM and a limit of detection of 62.38 nM under optimal conditions. Combined with a smartphone chromaticity analysis app, we designed a portable and disposable agarose hydrogel test kit using the proposed system, which realized the on-site semiquantitative and visual detection of SO3 2– in food samples.

Copper Immobilized over 2D Hexagonal SBA-15 for Electrochemical and Colorimetric Sulfite Sensing

“…This problem can be avoided by employing ethylenediaminetetraacetic acid as the chelating agent. 16 This outcome suggests that the colorimetric sulfite assay with our developed sensor has good selectivity. The selectivity of the colorimetric method was also investigated for different Scontaining analytes (such as bisulfite, bisulfate, HS − , cyclohexanethiol, 2-aminothiophenol, 1-dodecanethiol, and cysteine).…”

“…Whereas in the presence of a sulfite in the reaction medium (Figure S10b), Cu 2+ and Fe 3+ are the two cations that would most commonly obstruct the detection of sulfite because of their minimal impact on the absorbance at 652 nm. This problem can be avoided by employing ethylenediaminetetraacetic acid as the chelating agent . This outcome suggests that the colorimetric sulfite assay with our developed sensor has good selectivity.…”

“…Therefore, sulfite estimation has become necessary for ensuring the safety and quality of food as well as for protecting public health. Various techniques are available for sulfite detection using chromatography, spectrophotometry, electrochemical methods, colorimetry, chemiluminescence, flow injection analysis/gas diffusion, titration, etc. − However, most instrumental techniques are time-consuming, need experienced technicians, have significant running expenses, are labor-intensive, and have very low accuracy (particularly for low sulfite concentrations). Researchers are increasingly interested in electrochemical and colorimetric methods for sulfite sensing.…”

“…Since the report of Fe 3 O 4 NPs with peroxidase-like activity, several inorganic nanomaterials with enzyme-mimic activity have been explored. These include metal oxide nanomaterials, , mixed metal oxide nanomaterials, ,, graphene-based nanomaterials, , metal sulfides, , noble metals, , metal–organic frameworks, , and carbon nanotubes . These heterogeneous enzyme-mimic nanomaterials can compensate for deficiencies of natural enzymes and offer a wide range of applications, including biosensing, biocatalysis, medical diagnostics, and environmental cleanup.…”

Recent Advances in Design and Application of Nanomaterials-Based Colorimetric Biosensors for Agri-food Safety Analysis

“…Under the optimum conditions, the linear range of SO 3 2– detection was 1.56–15.58 μM, and the detection limit was 62.68 nM. Combined with mobile phone chromaticity analysis, on-site semiquantitative visual detection of SO 3 2– in food samples was be realized (Figure C) …”